The present invention relates to a metal melting furnace suitably used for melting or refining metals, in particular special steel.
A demand has recently been arisen to special steel to improve its quality, and a refinement aiming at degasification has been noticed.
As a representative for this degassing refinements, RH vacuum degassing technique has been known, but the RH vacuum degassing facility is large scaled. In addition to equipment cost, since the RH vacuum degassing facility has no special heating means, a problem arises that temperature is lowered during vacuum treating.
As an available vacuum treatment, there is a vacuum induction melting facility, and in general, this vacuum induction melting facility has a structure where the whole of a melting apparatus is completely received in a vacuum chamber, and accordingly the vacuum chamber is large. A facility is large scaled including incidental equipment, so that equipment cost is high.
Since in the vacuum induction melting facility, the induction heating coil is also received in the vacuum chamber, that is, since the induction heating coil is placed within the vacuum, the coil part is easy to discharge, and coil voltage should be 300 V or lower (though improving coil insulation, 600 V or lower). Therefore, in large scaled furnaces, it is difficult to in particular supply large electric power, and a problem is present about productivity.
For securing the productivity, a special electric source of large electric current type is necessary, and it is almost impossible to convert the high voltage type (small current type) to the vacuum induction furnace as maintaining the productivity.
The metal melting apparatus of the invention has been designed to settle such problems.
The metal melting apparatus of a first aspect of the invention is characterized in that a refractory furnace wall is furnished on an outer circumference thereof with a seal jacket of air tight and non-electrical conductivity, and disposed with vertical water cooling pipes along the inner circumference of the seal jacket at a predetermined distance with respect to one another, and the furnace casing is arranged at the outer part to encircle the furnace casing with an induction heating coil, and the furnace casing is secured to a frame by means of the seal jacket for reinforcing the structure. That is, the metal melting apparatus comprises:
(1) a furnace casing having a refractory furnace wall,
(2) an air-tight and non-electrical conductive seal jacket provided on an outer circumference of said refractory furnace wall,
(3) vertical water cooling pipes disposed along the inner circumference of said seal jacket, said pipes being arranged apart from one another at a predetermined interval,
(4) an induction heating coil arranged to encircle the furnace casing and disposed outside the furnace casing through space, and
(5) a frame secured to said seal jacket for supporting said furnace casing through said seal jacket.
The metal melting apparatus of a second aspect of the invention according to the first aspect, is characterized in that the seal jacket of the furnace casing is fixed to the frame at an upper end portion and a lower end portion via an upper flange and a lower flange.
The metal melting apparatus of a third aspect of the invention according to any one of the first or second aspect, is characterized in that the water cooling pipes comprise copper pipes, and are closely disposed in a circumferential direction at short pitch, wherein the distance between central positions of the pipes are within 3D, when the outer diameter or the length of one side of each water cooling copper pipe is D.
The metal melting apparatus of a fourth aspect of the invention according to any one of the second or third aspect, is characterized in that the water cooling pipes are attached and secured at upper and lower ends to the upper and lower flanges.
The metal melting apparatus of a fifth aspect of the invention according to any of the first to fourth aspects, is characterized in that a frame bed is provided, and said frame is rotatably provided to the frame bed together with the furnace casing.